Hello All,

I have a 70 mustang w/8" rear end. I recently built a 347 and would like to upgrade to a 9" positive traction w/lower gears. I have a 9" from a ford truck, not sure what year model, but I do know it is a big bearing rear end. I don't have the brakes with the truck axle, but I do have the backing plates. Anyone done this before and willing to share some advice? Thanks,

Barry

 

why not just buy a currie one and be done with it

 

That's the conclusion that I am coming to. I was just trying to save some money. I have a rear end with pumpkin and all from a ford truck. I figure it would be quite a bit cheaper to shorten the housing and buy the gears and posi unit. There seems to be a lot of variables involved in doing what I want to do. Currie wants $2500, which is a lot of money to me. It sure would save a lot of headache though.

Barry

 

Hi,

Look here: fordmuscle - 9 inch conversion

Though it's a conversion from small bearings 9'

 

Thanks,

I have seen this article, it is interesting, but I don't have all those mandrels and alignment bar and all that stuff that it takes to make that project work. I've come to the conclusion that I need to either be patient and find a rearend in an old car, or just shell out the bucks. It is really tempting to just put a posi unit in my 8", but I don't think it will hold up to 400+ hp. My better judgement tells me to wait and do it right the first time. Thanks for your time.

Barry

 

unless you ever shorten one before i wouldnt try it you could mess it up and the car will pull to one side and you forgot about have new axles made do you have a chop saw and a welder and a jig to make sure everything is straight

 

How hard did you build that 347? Unless you're over 400hp with a manual and doing a lot of clutch drops, I wouldn't worry about the 8 inch...they are a lot stronger than many people give them credit for.

 

+1

Back in when I was in high school, my dad dropped a warmed over 289/C4 with a 3500 stall converter and manual valve body into a '74 Pinto wagon that already had an 8 inch posi. It held up for over 5 years shifting at 7000 rpm(with the 4 bolt axles). Rust finally took the car off the road. It was light mettalic green with the wood grain sides with a luggage rack, quite the sight to watch that car smoke the tires through most of first gear and chirp them hard going into second and third...

Mike

 

an 8inch should hold up around 450 HP and torque.

 

Agree with the others. If everything is done right, the 8" should not be a problem.